1) Field of the Invention The invention relates to a process for determining the location of a positioning body in relation to a reference body 1 and a device for implementing the process.
2) Discussion of Related Art Such a process serves, e.g. to measure the distance between longitudinally moveable objects, like automatic measuring heads, gripping arms or assembly arms, during the control sequence of measuring and production machines. In so doing, the accuracy with which these distances can be determined is a decisive factor for the production accuracy of the automatic machines.
A process that enables high accuracy of measurement independently of an exact guide for the scanner is already known from the DE-OS 39 09 856. Here, three marks of a scale are evaluated by a scanner. With two marks, an angle of projection formed between a center of projection and these marks would still depend on the distance that the center of projection is above the marks and how far it is offset laterally. With three marks, however the center of projection can be determined exactly via the other angle of projection between the center of projection, the other mark and one of the other marks. For a combination of two combined angles there exists only one single place, at which the center of projection can be located.
In addition, it is known from the DE-PS 41 04 602 U.S. Pat. No. 5,401,226) to calculate the coordinates of the center of projection of an imaging lens from the known coordinates of marks on the scale via the projecting relationship between the projection surface of the scanner and the plane of the scale. The marks obtain their coordinate information with respect to the scale in coded form. The coordinate information is decoded during the calculation.
Furthermore, it is known from the book by G. Konecny and G. Lehmann: Photogrammetry, 4th edition, de Gruyter, Berlin--New York, 1984, pp. 48-55, to utilize a projecting relationship in order to determine the coordinates and to take into consideration an angle of tilt between a projection surface and the plane of the original image. To produce the projectivity between two planes, four known points are used.